Dye composition and the use of the same for dyeing powder coatings

ABSTRACT

The invention relates to a powdery dye composition consisting essentially of C.I. Pigment Red 170 (C.I. No. 12475) and barium sulfate, said barium sulfate being added before or during the production process of the C.I. Pigment Red 170. The inventive addition of barium sulfate enables non-homogeneities and caking to be avoided in the mixer.

The invention relates to an organic-inorganic colorant compositioncomprising barium sulfate and C.I. Pigment Red 170 and to its use forcoloring powder coating materials.

The preparation of powder coating materials is known and consistsessentially, as described in Farbe und Lack, 1986, 92, 734-737, of threeprocess steps. First of all the constituents of the powder coatingmaterial, such as binders, curing agents, colorants, and fillers, forexample, and also, where appropriate, auxiliary and additives, such ssurfactants, pigmentary and nonpigmentary dispersants, standardizers,resins, waxes, defoamers, antidust agents, extenders, preservatives,rheology control additives, wetting agents, antioxidants, UV absorbers,light stabilizers, antistats, devolatilizers, lubricants or acombination thereof, for example, are weighed out in accordance with theformula of the powder coating material, metered into a premix apparatus,and carefully mixed. In a second step the premix is suppliedcontinuously to an extruder and is melted and homogenized and the solidconstituents are dispersed by shearing. In the final step the melt,following its emergence from the extruder, is cooled rapidly in order tostop or prevent the reaction between binder and curing agent. Theextrudate is subsequently ground to the desired particle sizedistribution of the powder coating material.

This known and widely employed process has disadvantages particularly inthe first two steps. Thus during preparation of the premix and duringhomogenization in the extruder, inhomogeneities in the mixture and alsoinstances of caking are frequent occurrences. This results influctuations in quality and in inhomogeneities in the finished powdercoating material. A further disadvantage is the increased wear of thepremix apparatus and of the extruder owing to the greater mechanicalload imposed by such inhomogeneities and agglomerations. Another greatdisadvantage lies in the partial loss of the raw materials used. Theincreased cleaning effort is also considered a disadvantage.

In order to overcome the stated disadvantages, modified processes areemployed in part for the first process step, i.e., the premixing of theindividual constituents of the powder coated material, and in part forthe second process step, i.e., that of melting, homogenizing, anddispersing in the extruder. Some processes feature modification of bothprocess steps in order to optimize powder coating preparation.

Thus, for example, DE-A-4 101 048 describes a modified process forpreparing a powder coating material, in which the binder component andcuring component are premixed, supplied continuously to the extruder,and melted in the extruder. Pigments, fillers, and further constituentsare premixed separately and metered into the extruder at the end of themelting zone or in the downstream homogenizing and/or dispersing zone.

A disadvantage with this process for the powder coatings manufacturer isthat a second premix apparatus is required and in effect a furtherprocess step is implemented, giving rise to costs through additionalrequirement for space, time, and capital. A further disadvantage of theprocess cited is that even with the separate premixing of pigment,fillers, and any further constituents it is possible for inhomogeneitiesand instances of caking to occur.

U.S. Pat. No. 3,790,513 discloses a process for dispersing allconstituents of the powder coating material in an organic solvent andsupplying this mixture to a vacuum extruder. As a result of supply ofheat and application of a vacuum, first of all the organic solvent isevaporated, and subsequently the mixture is homogenized and dispersed bymelt extrusion. Disadvantages associated with this process are thecostly evaporation of the organic solvent and the additional technicalcomplexity this procedure necessitates.

U.S. Pat. No. 4,320,048 describes a process in which all of thecomponents of the powder coating material except for the colorant arepremixed and supplied to the extruder. The colorant is fed to theextruder separately from this premix, in the form of a dispersion andcontaining up to 60% by weight of an organic solvent, and then in theextruder is mixed with the other components. Although this processrequires a quantity of solvent which is lower in percentage terms, inrespect of the finished powder coating material, than that described inU.S. Pat. No. 3,790,513, the need to remove the solvent from the powdercoating mixture is a disadvantage here as well.

WO 91/13931 describes a process for preparing pigment concentrates(masters) and the suitability thereof for coloring powder coatingmaterials. The master is prepared from a mixture of colorant(s),optionally filler(s), wetting agent(s), polymer vehicle(s), and, whereappropriate, further additive(s) in an “adiabatic” high-speed mixer, thecomposition being melted as a result of the frictional heat produced andbeing homogenized and dispersed. Such masters can be used as colorantsfor preparing powder coating materials, the powder coating beingobserved to have an improved homogeneity, a greater color strength, andan improved leveling and gloss compared to the conventionalincorporation of the colorant. A disadvantage here is that an additionalprocess step is needed, namely the preparation of the master in anadditional apparatus, a specialty high-speed mixer. This hasdisadvantageous consequences for the costs and time required for powdercoating preparation. A further disadvantage is that a colorant productof this kind includes a multiplicity of additives, whose effect on thepowder coating manufacturer's coating systems is unpredictable.

Organic-inorganic colorant preparations are known, for example, from EP0 702 055, EP 0 702 063 and EP 0 845 504. The pigment products describedtherein, with natural and synthetic silicates as inorganic fillingmaterial, are indeed referred to as “stir-in” pigments, but do not meetthe requirements already described with regard to the premix onincorporation into powder coating systems. Examples given of natural andsynthetic silicates include mica, kaolin, and talc.

Pigment Red 170 (C.I. 12475) is one of the major colorants forpigmenting powder coating materials in the neutral red range. Inaddition to its heat resistance it has the particular feature ofoutstanding fastness to blooming in powder coating systems. Because oftheir tendency to bloom, for example, the more yellow-toned Pigment Red112 (C.I. 12370) has only limited suitability, and Pigment Red 3 (C.I.12120) no suitability at all, for this area of application. Otherpigments which are likewise similar coloristically to Pigment Red 170are incapable of unrestrictedly replacing this pigment in powder coatingsystems, owing to other important performance properties, such asdeficient fastness in exterior application, poor hiding power orinadequate color strength, for example.

From experience, however, it is known that with Pigment Red 170 inparticular there are instances of inhomogeneity and caking to a highdegree when the pigment is incorporated into powder coating systems,particularly in connection with the preparation of the premix.

It is an object of the present invention, then, to provide a materialwhich comprises essentially Pigment Red 170 and which can beincorporated into powder coating systems by simple mixing in a premixapparatus without causing inhomogeneities or instances of caking. It isa further object of the invention to provide this material asinexpensively as possible, i.e., without additional process steps incomparison to conventional pigment powders. Moreover, the material oughtto minimize the cleaning effort associated with a change of shade in thepremix apparatus, and also its wear.

It has now been found that this object, surprisingly, has beenachievable by defined addition of barium sulfate to Pigment Red 170.

The present invention provides a powderous colorant compositionconsisting essentially of C.I. Pigment Red 170 (C.I. No. 12475) andbarium sulfate, the latter having been added before or during theoperation of preparing C.I. Pigment Red 170.

The additive is added during any desired operating step which is to berun through during pigment preparation, and produces as a result apigment preparation which, unlike a dry mix of the finished pigment withbarium sulfate, can be incorporated directly into powder coating systemswithout problems and without introduction of further operating steps.

The operation of preparing the pigment normally embraces its synthesis,i.e., diazotization of 4-carbamoyl-aniline and coupling of the diazoniumsalt with 3-hydroxy-N-(2′-ethoxyphenyl)-2-naphthoamide, its isolation asa presscake, and the cleaning thereof by washing, optionally the pastingor slurrying of the washed presscake, finishing of the resultantsuspension by thermal treatment, isolation of the finished presscake andthe cleaning thereof by washing, and, where appropriate, granulation ofthe finished and washed presscake. This is followed by drying of thegranules and grinding thereof to the pigment powder. The barium sulfateis added prior to this drying step, at the latest. By way of example thebarium sulfate can be added before or during pigment synthesis orimmediately before or during a subsequent finish. The barium sulfate canalso of course be added in portions at different times.

By finishing the skilled worker means a thermal aftertreatment of themoist crude pigment, obtained after synthesis, in a finished medium,e.g., in water, an organic solvent or a mixture of water and organicsolvent, it being necessary for the water and the organic solvent to bemiscible with one another neither at room temperature nor at any othertemperature, in order to produce a particle size distribution and/orcrystal form and/or crystal polymorph that is specific for theapplication. Temperatures arising in this operation may range, forexample, from 0 to 200° C.

The barium sulfate is preferably added immediately before or after thefinish in an aqueous, aqueous-alkaline, aqueous-acidic, aqueous-organicor organic medium. The barium sulfate can also be added to thewater-moist presscake prior to drying and incorporated, in which casethe barium sulfate can itself be used likewise in dry form or in theform of a water-moist presscake.

The proportions between pigment and barium sulfate can vary within wideranges.

Advantageously the colorant composition of the invention consists offrom 60% to 99% by weight, preferably from 70% to 95% by weight, andvery preferably from 80% to 90% by weight of C.I. Pigment Red 170 andfrom 1% to 40% by weight, preferably from 5% to 30% by weight, and verypreferably from 10% to 20% by weight of barium sulfate.

The colorant preparation of the invention advantageously possesses aunimodal primary particle size distribution (D_(50%)), as determined byevaluating transmission electron micrographs, of between 0.1 μm and 1.5μm, preferably between 0.15 μm and 0.40μm.

The present invention also provides a process for preparing the colorantcomposition of the invention, which comprises adding barium sulfatebefore or during the operation of preparing C.I. Pigment Red 170, andhomogenizing the mixture.

In order to achieve sufficient premixing or predispersing of the PigmentRed 170 in the binder of the powder coating material and in order toobtain optimum performance properties, the barium sulfate ought to havean average particle size (d₅₀) of from 10 to 0.1 μm. Preference is givento barium sulfates having an average particle size of from 5 to 0.5 μm,more preferably those having an average particle size of from 1.5 to 0.7μm.

The pigment preparations of the invention feature outstanding coloristicand rheological properties, in particular an outstanding rheology, hightransparency and brightness, and great ease of dispersing. They areespecially suitable for use in powder coating materials, but also ascolorants for contactless printing techniques, such as inelectrophotographic toners and ink-jet inks, for example.

The pigment preparation of the invention can be used in any proportionnecessary for the coloring of powder coating materials. In respect ofthe material to be colored it is usual to use from 0.1% to 30% byweight, preferably from 0.5% to 20% by weight and very preferably from1% to 10% by weight of the pigment preparation of the invention.

For the coloring of a powder coating mixture the pigment preparation ofthe invention can be used on its own. In order to produce differentshades or color effects it is also possible to add further colorants,such as white, colored or black pigments, for example, and also effectpigments, to the powder coating mixture.

Binders used for powder coating materials are typically epoxy resins,optionally carboxyl- and/or hydroxyl-containing polyester resins,polyurethane resins, and acrylic resins, together with the usual curingagents. Combinations of resins are also employed. For example, epoxyresins are frequently used in combination with carboxyl- andhydroxyl-containing polyester resins. Typical curing components(preferably from 3% to 10% by weight, based on the resin) are, forexample, acid anhydrides, imidazoles, and also dicyandiamide and itsderivatives, blocked isocyanates, bisacylurethanes, phenolic andmelamine resins, triglycidyl isocyanurates, oxazolines, and dicarboxylicacids.

The present invention further provides a powder coating formulationcomprising the pigment preparation of the invention and also a customarybinder.

Preference is given to powder coating materials consisting essentiallyof from 0.1% to 30% by weight, in particular from 0.5% to 20% by weight,more preferably from 1% to 10% by weight, of the pigment preparation ofthe invention, from 45% to 80% by weight, in particular from 50% to 70%by weight, more preferably from 55% to 65% by weight, of a binder(including curing agent) from the group consisting of epoxy resins,polyester resins, polyurethane resins, acrylate resins, or a combinationof these resins, and from 0% to 50% by weight of further additives, suchas, for example, shading colorants, surfactants, fillers, charge controlagents for controlled setting of the electrostatic charge, dispersants,standardizers, waxes, defoamers, antidust agents, extenders,preservatives, rheology control additives, wetting agents, antioxidants,UV absorbers, light stabilizers, antistats, lubricants ordevolatilizers.

The invention additionally provides a process for preparing a powdercoating formulation, which comprises mixing the pigment preparation ofthe invention, the binder, and, where appropriate, the additives,extruding the mixture, and cooling and grinding the extrudate.

The powder coating formulations of the invention may betriboelectrically or electrokinetically sprayable powder coatingmaterials and may be employed for coating the surfaces of articles madefrom, for example, metal, wood, plastic, glass, ceramic, concrete,textile material, paper or rubber (J.F. Hughes, “Electrostatic PowderCoating” Research Studies, John Wiley & Sons, 1984).

In order to assess the properties of the pigment preparations in thepowder coatings sector the pigment preparations were incorporated into apolyester/TGIC binder system; first of all the various constituents ofthe powder coating material, i.e., PE/TGIC Crylcoat, leveling agents,devolatilizers, fillers, and the pigment preparation of the invention,were mixed in a high-speed mixer (e.g., Mixaco Container Mixer LAB CM)for 180 seconds. Thereafter a visual assessment was made of the degreeof caking and deposits, and the effort required to clean the mixer wasalso assessed.

Assessment of the coloristic properties of the pigment preparations tookplace in an alkyd-melamine resin varnish (AM 5) and followingincorporation into a polyester/TGIC binder system, dispersion of themixture in a kneading apparatus, grinding of the extrudate,classification by sieving, spraying of the powder coating mixture onto asubstrate, and formation of a uniform coating film by thermalcrosslinking at 200° C.

The particle size distributions (primary particles) of the products weredetermined by visual analysis of transmission electron micrographs ofthe sample in question.

The particle size distributions of the inorganic substances used weretaken from the product description of the respective manufacturer.

In the examples below parts are in each case parts by weight andpercentages in each case percentages by weight. “min” are minutes.

EXAMPLE 1a

3 600 parts of aqueous finish suspension containing approximately 273parts of C.I. Pigment Red 170 are admixed with 67.5 parts of syntheticbarium sulfate (®Blanc Fixe HD 80 from Solvay Soda GmbH, Rheinberg)having an average particle diameter (d_(50%)) of 1 μm and the suspensionis stirred for 10 min and then adjusted to pH>11.0 using 33% strengthsodium hydroxide solution. The bright red product is filtered, washedwith water, dried in a forced air cabinet at 100° C., and finally groundusing a laboratory mill, with cooling. This gives approximately 340parts of a pigment preparation which in the AM 5 varnish producestransparent ultraclean coatings of high color strength. Determination ofthe primary particle size distribution reveals a mean particle size(d_(50%)) of 0.235 μm.

EXAMPLE 1b

61.83 parts of ®Crylcoat 2988 (carboxylated polyester resin), 4.65 partsof ®Araldit PT 810 (TGIC curing agent), 3.32 parts of ®Additol XL 496(leveling agent), 0.20 parts of benzoin (devolatilizer), 20.00 parts ofBlanc Fixe N (BaSO₄), 5.00 parts of titanium dioxide Kronos 2310(filler), and 5.00 parts of pigment preparation prepared in accordancewith example 1a are weighed into a vessel and subsequently introducedinto a high-speed laboratory mixer. Mixing is then carried out at 2 000rpm for 3 min, without cooling. Inspection after the mixer has beenemptied shows that there are virtually no deposits on the vessel wall oron the mixing paddle. Cleaning of the mixer is easy and quick.

EXAMPLE 2 (COMPARATIVE EXAMPLE)

The procedure of example 1b is repeated, but using as colorant 5.00parts of standard commercial C.I. Pigment Red 170 instead of the pigmentpreparation described under example 1a. Inspection after mixing revealssevere deposits and sticking on the walls of the mixer and on the mixingpaddle itself. Cleaning of the high-speed laboratory mixer is laboriousand time-consuming.

EXAMPLE 3a (COMPARATIVE EXAMPLE)

A mixture of 1 500 parts of water and 80 parts of 80% strength aceticacid is cooled with ice to 10° C. and admixed with a hydrochloric acidsolution of 126.4 parts of 4-carbamoylbenzenediazonium hydrochloride andsmall amounts of sodium nitrite. The excess nitrite is destroyed usingamidosulfonic acid. Subsequently a clarified solution of 244.4 parts of3-hydroxy-N-(2′-ethoxyphenyl)-2-naphthoamide and 156.4 parts of a 33%strength sodium hydroxide solution in 1 500 parts of water is addeddropwise over the course of 120 min. When coupling is complete stirringis continued for 30 min and then the pH is adjusted with 173 parts of31% strength hydrochloric acid and the reaction mixture is heated withsteam to 98° C. After 4 h at this temperature it is cooled with water to70° C., admixed with 204 parts of 33% strength sodium hydroxidesolution, and stirred for a further 5 min, and the bright red solid isisolated by filtration. The filter cake is washed carefully with water,dried in a forced air cabinet at 120° C., and ground using an air jetmill.

EXAMPLE 3b (COMPARATIVE EXAMPLE)

1 410 parts of the pigment thus prepared are mixed mechanically with 340parts of synthetic barium sulfate with an average particle size(d_(50%)) of 1.0 μm (Blanc Fixe HD 80 from Solvay Soda GmbH, Rheinberg).

The resulting pigment preparation is incorporated in accordance withexample 1b into a powder coating mixture. Examination reveals theformation of deposits which are greater than those of example 1b.

EXAMPLE 4

An acetate-buffered solution of 0.6 mol of 4-carbamoylbenzenediazoniumhydro-chloride in water is admixed with stirring with 0.29 mol ofsynthetic barium sulfate (Blanc Fixe HD 80 from Solvay) having anaverage particle diameter (d_(50%)) of 1 μm.

Subsequently a clarified alkaline-aqueous solution of 0.65 mol of3-hydroxy-N-(2′-ethoxyphenyl)-2-naphthoamide is run in over the courseof 130 min. When coupling is complete stirring is continued for 15 min.The reaction suspension is filtered and washed with water. Theintense-red presscake obtained is stirred together with water and madeup to a volume of 3 600 ml. The suspension is adjusted to a pH of 3.8using acetic acid and stirred at 102° C. for an hour. After thissuspension has cooled to room temperature it is admixed with 30 ml of33% strength sodium hydroxide solution and stirred for 30 min and thenthe red product is isolated by filtration. The presscake is washed withwater, dried in a forced air cabinet at 100° C., and finally groundusing a laboratory mill, with cooling. This gives 340 g of pigmentpreparation which in the AM 5 varnish gives transparent ultracleancoatings of high color strength.

EXAMPLE 5

1 421 parts of unfinished water-moist presscake containing 270 parts ofC.I. Pigment Red 170 crude are diluted with water to a volume of 5 000ml and the suspension is adjusted to a pH of 3.8 using 50% strengthacetic acid, with stirring. Subsequently 76.5 parts of synthetic bariumsulfate (Blanc Fixe HD 80 from Solvay Soda GmbH, Rheinberg) having anaverage particle diameter (d_(50%)) of 1 μm are added and the mixture ishomogenized for 10 min with stirring and then heated with low-pressuresteam to 98° C. After 2 h a third of the suspension is withdrawn, cooledto 70° C. with water, and adjusted to a pH>10 using 33% strength sodiumhydroxide solution. Stirring is continued for 10 min and then the brightred product is isolated by filtration, washed with water, dried in aforced air cabinet at 100° C., and finally ground using a laboratorymill, with cooling. This gives 80 g of a pigment preparation which inthe AM 5 varnish gives transparent ultraclean coatings of high colorstrength.

EXAMPLE 6a

1 385 parts of unfinished water-moist presscake containing 270 parts ofC.I. Pigment Red 170 crude are diluted with water to a solidsconcentration of approximately 7% and the suspension is adjusted to a pHof 3.8 using 80% strength acetic acid, with stirring. Thereafter theaqueous pigment suspension is heated to 105° C. with stirring and isheld at this temperature for an hour. After the suspension has cooled itis admixed with 67.5 parts of synthetic barium sulfate having a meanparticle diameter of 0.7 μm (Blanc Fixe Micro from Sachtleben Chemie,Duisburg) and homogenized for 10 min with stirring. The pH is adjustedto a level above 10 by addition of 33% strength sodium hydroxidesolution and the suspension is stirred for 30 min more and finally isfiltered. The bright red filter residue is carefully washed with water,dried at 100° C. in a forced air cabinet, and finally ground using anair jet mill. This gives a pigment preparation which in the AM 5 varnishgives transparent ultraclean coatings of high color strength.Determination of the primary particle size distribution reveals a meanparticle size (d_(50%)) of 0.230 μm.

EXAMPLE 6b

61.83 parts of Crylcoat 2988 (carboxylated polyester resin), 4.65 partsof Araldit PT 810 (TGIC curing agent), 3.32 parts of Additol XL 496(leveling agent), 0.20 parts of benzoin (devolatilizer), 20.00 parts ofBlanc Fixe N (filler), 5.00 parts of titanium dioxide Kronos 2310(filler) and 5.00 parts of pigment preparation prepared in accordancewith example 6a are weighed out into a vessel and subsequentlyintroduced into a Mixaco Container Mixer LAB CM 3-D. These componentsare subsequently mixed at 2 000 rpm (dispersion paddle) or 330 rpm(mixing paddle) for 3 min without cooling. Inspection of the Mixacomixer after it has been emptied reveals virtually no deposits on thecontainer wall (mixing vessel), on the mixing paddle or on thedispersion paddle. Cleaning of the mixer is easy and quick. Incomparison to a mixture prepared using standard commercial C.I. PigmentRed 170 the level of deposits formed is significantly lower.

EXAMPLE 7a (COMPARATIVE EXAMPLE)

The procedure of example 6a is repeated, but replacing the bariumsulfate by 67.5 parts of Clay ASP-Ultrafine (Chemie-Mineralien GmbH &Co. KG, Bremen) having a mean particle diameter (d_(50%)) of 0.2 μm.Determination of the primary particle size distribution reveals a meanparticle size (d_(50%)) of 0.262 μm.

EXAMPLE 7b

The pigment preparation obtained from example 7a is incorporated inaccordance with example 6b into a powder coating mixture. Inspectionafter the Mixaco mixer has been emptied reveals a significantly greaterlevel of deposits on the container wall (mixing vessel), on the mixingpaddle, and on the dispersion paddle than when using the pigmentpreparation from example 6a.

EXAMPLE 8a (COMPARATIVE EXAMPLE)

The procedure of example 6a is repeated, but replacing the bariumsulfate by 67.5 parts of chalk having a mean particle diameter of 2.7 μm(Millicarb-OG from Omya GmbH, Cologne). Determination of the primaryparticle size distribution reveals a mean particle size (d_(50%)) of0.251 μm.

EXAMPLE 8b (COMPARATIVE EXAMPLE)

The pigment preparation obtained from example 8a is incorporated inaccordance with example 6b into a powder coating mixture. Inspectionafter the Mixaco mixer has been emptied reveals a significantly greaterlevel of deposits on the container wall (mixing vessel), on the mixingpaddle, and on the dispersion paddle than when using the pigmentpreparation from example 6a.

EXAMPLE 9a

The procedure of example 6a is repeated, but replacing the syntheticbarium sulfate having a mean particle diameter of 0.7 μm (Blanc FixeMicro from Sachtleben Chemie, Duisburg) by 67.5 parts of heavy sparhaving a mean particle diameter of 1.0 μm (Albawhite from SachtlebenChemie, Duisburg). This gives a pigment preparation which in the AM 5varnish gives transparent ultraclean coatings of high color strength.Determination of the primary particle size distribution reveals a meanparticle size (d_(50%)) of 0.246 μm.

EXAMPLE 9b

The pigment preparation obtained from example 9a is incorporated inaccordance with example 6b into a powder coating mixture. Inspectionafter the Mixaco mixer has been emptied reveals only minimal deposits onthe container wall (mixing vessel), on the mixing paddle, and on thedispersion paddle.

EXAMPLE 10a (COMPARATIVE EXAMPLE)

The procedure of example 6a is repeated, but replacing the bariumsulfate by 67.5 parts of mica having a mean particle diameter of <2.0 μm(Mica SFG70 from Aspanger Bergbau and Mineralwerke GmbH, Aspang,Austria). Determination of the primary particle size distributionreveals a mean particle size (d_(50%)) of 0.240 μm.

EXAMPLE 10b (COMPARATIVE EXAMPLE)

The pigment preparation obtained from example 10a is incorporated inaccordance with example 6b into a powder coating mixture. Inspectionafter the Mixaco mixer has been emptied reveals a significantly greaterlevel of deposits on the container wall (mixing vessel), on the mixingpaddle, and on the dispersion paddle than when using the pigmentpreparation from example 6a.

EXAMPLE 11a (COMPARATIVE EXAMPLE)

The procedure of example 6a is repeated, but replacing the bariumsulfate by 67.5 parts of talc having a mean particle diameter of 4.5 μm(Finntalc M 15 from Omya GmbH, Cologne). Determination of the primaryparticle size distribution reveals a mean particle size (d_(50%)) of0.268 μm.

EXAMPLE 11b (COMPARATIVE EXAMPLE)

The pigment preparation obtained from example 11a is incorporated inaccordance with example 6b into a powder coating mixture. Inspectionafter the Mixaco mixer has been emptied reveals a significantly greaterlevel of deposits on the container wall (mixing vessel), on the mixingpaddle, and on the dispersion paddle than when using the pigmentpreparation from example 6a.

EXAMPLE 12a (COMPARATIVE EXAMPLE)

The procedure of example 6a is repeated, but replacing the bariumsulfate by 67.5 parts of marble having a mean particle diameter of 0.9μm (Calcigloss-GU from Omya GmbH, Cologne). Determination of the primaryparticle size distribution reveals a mean particle size (d_(50%)) of0.250 μm.

EXAMPLE 12b (COMPARATIVE EXAMPLE)

The pigment preparation obtained from example 12a is incorporated inaccordance with example 6b into a powder coating mixture. Inspectionafter the Mixaco mixer has been emptied reveals a significantly greaterlevel of deposits on the container wall (mixing vessel), on the mixingpaddle, and on the dispersion paddle than when using the pigmentpreparation from example 6a.

EXAMPLE 13a (COMPARATIVE EXAMPLE)

The procedure of example 6a is repeated, but replacing the bariumsulfate by 67.5 parts of talc having a mean particle diameter of 1.1 μm(Talk A-3 from Naintsch Mineralwerke, GmbH, Graz, Austria).

EXAMPLE 13b (COMPARATIVE EXAMPLE)

The pigment preparation obtained from example 13a is incorporated inaccordance with example 6b into a powder coating mixture. Inspectionafter the Mixaco mixer has been emptied reveals a significantly greaterlevel of deposits on the container wall (mixing vessel), on the mixingpaddle, and on the dispersion paddle than when using the pigmentpreparation from example 6a.

EXAMPLE 14a (COMPARATIVE EXAMPLE)

The procedure of example 6a is repeated, but replacing the bariumsulfate by 67.5 parts of dolomite having a mean particle diameter of 2.5μm (Microdul Super from Omya GmbH, Cologne). Determination of theprimary particle size distribution reveals a mean particle size(d_(50%)) of 0.229 μm.

EXAMPLE 14b (COMPARATIVE EXAMPLE)

The pigment preparation obtained from example 14a is incorporated inaccordance with example 6b into a powder coating mixture. Inspectionafter the Mixaco mixer has been emptied reveals a significantly greaterlevel of deposits on the container wall (mixing vessel), on the mixingpaddle, and on the dispersion paddle than when using the pigmentpreparation from example 6a.

1. A powderous colorant composition consisting essentially of C.I.Pigment Red 170 (C.I. No. 12475) and barium sulfate, wherein the bariumsulfate has been added before or during preparation of C.I. Pigment Red170.
 2. A colorant composition as claimed in claim 1, consistingessentially of from 60% to 99% by weight of C.I. Pigment Red 170 andfrom 1% to 40% by weight of barium sulfate.
 3. A colorant composition asclaimed in claim 1 having a particle size distribution (D_(50%)) ofbetween 0.1 μm and 1.5 μm.
 4. A process for preparing a colorantcomposition as claimed in claim 1, comprising the steps of adding bariumsulfate before or during the preparation of C.I. Pigment Red 170, andhomogenizing the mixture.
 5. The process as claimed in claim 5, whereinthe barium sulfate is added during the synthesis of C.I. Pigment Red 170and/or immediately before, during and/or immediately after a finish ofC.I. Pigment Red 170 crude pigment.
 6. The process as claimed in claim5, wherein the barium sulfate is added after the finish of the C.I.Pigment Red 170 crude pigment but before the C.I. Pigment Red 170 crudepigment is dried.
 7. The process as claimed in one claim 4, wherein thebarium sulfate has a particle size distribution (d_(50%)) of between 0.1μm and 10 μm.
 8. A powder coating material colorant comprising acolorant composition as claimed in claim
 1. 9. A powder coatingformulation comprising a colorant composition as claimed in claim 1 anda binder.
 10. A powder coating formulation as claimed in claim 9,consisting essentially of from 0.1% to 30% by weight of the colorantcomposition, from 45% to 80% by weight of a binder, wherein the binderincludes a curing agent, wherein the binder is selected from the groupconsisting of epoxy resins, polyester resins, polyurethane resins,acrylate resins, and combinations thereof, and from 0% to 50% by weightof at least one additive selected from the group consisting of shadingdyes, surfactants, fillers, charge control agents for controlled settingof the electrostatic charge, dispersants, standardizers, waxes,defoamers, antidust agents, extenders, preservatives, rheology controladditives, wetting agents, antioxidants, UV absorbers, lightstabilizers, antistats, lubricants and devolatilizers.
 11. A process forpreparing a powder coating formulation as claimed in claim 9 comprisingthe steps of mixing the colorant composition and the binder to form amixture, extruding the mixture to form an extrudate, and cooling andgrinding the extrudate.
 12. The process as claimed in 11, furthercomprising adding at least one additive to the mixture.
 13. Anelectrophotographic toner colorant comprising a colorant composition asclaimed in claim 1.